An Activated ras ^N Gene: Detected in Late But Not Early Passage Human PA1 Teratocarcinoma Cells

Abstract

Early passages of the human teratocarcinoma cell line PA1 are not tumorigenic in nude mice, while late passages are. A transforming gene present in late passages of PA1 cells was isolated as a biologically active molecular clone and is a new isolate of the human rasN locus. Its transforming activity is due to a single G---A (G, guanine; A, adenine) point mutation at the codon for amino acid 12 which changes the codon for glycine so that an aspartic acid residue is expressed. In contrast to late passage PA1 cells (passages 106, 330, and 338), DNA from the PA1 cell line at early passages (passage 36) does not yield rasN foci in DNA transfection assays. Thus, the presence of an activated rasN in PA1 cells correlates with enhanced tumorigenicity of the cell line and, more importantly, may have arisen during cell culture in vitro.

The class II tumour suppressor gene H-REV107-1 is a target of interferon-regulatory factor-1 and is involved in IFNγ-induced cell death in human ovarian carcinoma cells

“…We identi®ed two di erent modes of H-REV107-1 regulation in established ovarian cell lines: The gene is completely down-regulated in KRAS-transformed A2/5 rat ovarian epithelial cells and partially repressed in human PA1 ovarian teratocarcinoma cells which express a mutated NRAS gene (Tainsky et al, 1984). Down-regulation of the H-REV107-1 gene is dependent on activated MAP/ERK signalling, since expression is restored (A2/5) or elevated (PA1) in the presence of the MEK inhibitor PD98059.…”

“…To ®nd out whether down-regulation of the H-REV107-1 gene in human ovarian carcinomas also depends on signal transduction pathways downstream of RAS, we investigated mRNA levels in seven human ovarian carcinoma cell lines following inhibition of the MAP/ ERK or the PI-3 kinase pathway. H-REV107-1 is partially suppressed via an activated MAP/ERK pathway only in the PA1 ovarian teratocarcinoma cell line which harbours an activated NRAS oncogene (Figure 2c) (Tainsky et al, 1984), but not in any of the other epithelial carcinoma cell lines. These results show that both the rat and the human H-REV107-1 genes can be a target of activated RAS oncogenes, irrespective of the RAS isoform.…”

Malignant progression of an SV40-transformed human epidermal keratinocyte cell line

“…The results described in this paper, together with a previous report (Tainsky et al, 1984) indicate that profound genetic changes may occur spontaneously during the in vitro cultivation of human cells, and therefore caution is indicated in interpreting the results from so-called '2-stage' in vitro models where multiple genes or agents have been used, since conversion of SV6-1 transformed normal keratinocytes to a malignant phenotype may have represented several spontaneous events.…”

“…We are now investigating whether there is any evidence of ras gene activation in high passage SV6-1 Bam/HFK cells. Spontaneous activation of the N-ras proto-oncogene has been previously demonstrated following in vitro cultivation of a human teratocarcinoma cell line (Tainsky et al, 1984).…”

Molecular cloning and characterization of an activated human c-raf-1 gene.

“…An activated Ki-ras gene was demonstrated in a metastatic variant of a mouse T-lymphoma cell line, but not in the parental cell line (38). An activated N-ras gene was detected in a human teratocarcinoma cell line at late but not early passages (34). Tumor cells are so-called hypermutable cells and are thought to have various genetic rearrangements.…”